The fan arranged in the tool is covered by a fan housing connected to the housing of the tool by means of threaded fasteners. The fan housing has a forward fan screen and a rearward intake opening. The fan screen is configured so as to be as large as possible for obtaining a reduced in-flow velocity in the plane of the fan screen. For this reason, a deflector section is arranged between the fan screen and the fan for bridging the diameter difference between the inlet surface of the fan screen and the effective intake cross section of the fan.
It is known to produce the outer fan housing with the fan screen as an injection molded part preferably made of plastic and to then attach the deflecting section in the fan housing as an assembly part. This configuration assures that for the injection molding process, the windows of the fan screen formed by struts and transverse struts can be formed to have the same size. A one-piece configuration of the fan housing, fan screen and the deflector section cannot, however, be obtained with a constant window size in the fan screen.